Fuel cells can be configured in numerous ways with a variety of electrolytes, fuels and operating temperatures. For example, fuels such as hydrogen or methanol can be provided directly to the fuel cell electrode or fuels such as methane or methanol can be converted to a hydrogen rich gas mixture external to the cell itself and subsequently provided to the fuel cell. Air is the source of oxygen in most fuel cells, although in some applications the oxygen is obtained by hydrogen peroxide decomposition or from a cryogenic storage system.
Simple fuel cells have the anode reaction: EQU H.sub.2 .fwdarw.2H.sup.+ +2 e.sup.-
and as a cathode reaction: EQU 1/2 O.sub.2 +2 H.sup.+ +2 e.sup.- .fwdarw.H.sub.2 O
Although there are theoretically a limitless number of combinations of electrolyte, fuel, oxidant, temperatures and so on, practical systems include aqueous acid electrolyte systems using hydrogen as a fuel and air as the oxygen source; phosphoric acid electrolyte systems using indirect methanol or hydrocarbons as the fuel and pure oxygen as the oxidant; and solid polymer electrolyte systems using hydrogen or hydrazine as the fuel source and pure oxygen as the oxidant. Solid polymer electrolyte fuel cells sometimes include a sulfonated polyfluoroolefin (Nafion.TM., manufactured by DuPont) membrane.
The performance, high cost and processability of suitable polymeric electrolyte materials are all important considerations in fuel cell construction. While sulfonated polybenzimidazole polymers are known, see for example U.S. Pat. No. 4,814,399 and it is further known in the art to imbibe polybenzimidazole membranes with a strong acid to make a proton conducting media, performance in terms of conductivity, processability, costs, stability under operating conditions and so on remain significant issues with respect to polymeric media for fuel cells.